The Regulatory Role of Ferric Uptake Regulator (Fur) during Anaerobic Respiration of Shewanella piezotolerans WP3

Ferric uptake regulator (Fur) is a global regulator that controls bacterial iron homeostasis. In this study, a fur deletion mutant of the deep-sea bacterium Shewanella piezotolerans WP3 was constructed. Physiological studies revealed that the growth rate of this mutant under aerobic conditions was only slightly lower than that of wild type (WT), but severe growth defects were observed under anaerobic conditions when different electron acceptors (EAs) were provided. Comparative transcriptomic analysis demonstrated that Fur is involved not only in classical iron homeostasis but also in anaerobic respiration. Fur exerted pleiotropic effects on the regulation of anaerobic respiration by controlling anaerobic electron transport, the heme biosynthesis system, and the cytochrome c maturation system. Biochemical assays demonstrated that levels of c-type cytochromes were lower in the fur mutant, consistent with the transcriptional profiling. Transcriptomic analysis and electrophoretic mobility shift assays revealed a primary regulation network for Fur in WP3. These results suggest that Fur may act as a sensor for anoxic conditions to trigger and influence the anaerobic respiratory system.

铁摄取调控因子（Ferric uptake regulator，Fur）是调控细菌铁稳态的全局性调控因子。本研究构建了深海耐压希瓦氏菌WP3（Shewanella piezotolerans WP3）的fur基因缺失突变株。生理实验结果显示，该突变株在有氧条件下的生长速率仅略低于野生型菌株（wild type，WT），但在厌氧条件下添加不同电子受体（electron acceptors，EAs）时，却出现了严重的生长缺陷。比较转录组学分析表明，Fur不仅参与经典的铁稳态调控过程，还参与厌氧呼吸的调控。Fur通过调控厌氧电子传递系统、血红素生物合成系统以及细胞色素c成熟系统，对厌氧呼吸发挥多效性调控作用。生化测定结果证实，fur突变株中的c型细胞色素水平显著降低，这与转录组学分析结果相符。转录组学分析与电泳迁移率变动分析（electrophoretic mobility shift assay，EMSA）揭示了WP3菌株中Fur的核心调控网络。上述研究结果表明，Fur或可作为缺氧感应因子，触发并调控厌氧呼吸系统。